Monday, March 20, 2006

How Robertson got Betamaxed

The Pythagorean philosopher Archytas of Tarentum (5th century BC) is the alleged inventor of the screw. Screws came into common use around the 1st century BC. These were the wooden screws that were used in wine presses, olive oil presses and for pressing clothes. Metal screws and nuts only appeared in the 15th century. 16th-century screw-making was a cottage industry. The threads, filed by hand, were imperfect and shallow, and screws were so expensive that they were sold individually. In the 18th century, industrialization brought consumers mass-produced screws at cheaper prices, but they still had one drawback: The machinery of the day couldn't file a screw to a point. Workers had to drill a hole into material to get the blunt screw-end started. The familiar machine-made, pointed self-starting screw didn't appear until the mid-19th century.

The effort to find a superior head is an interesting story in its own right. From 1860 to 1890, the author discovered, American screw manufacturers explored numerous solutions, including magnetic screwdrivers and double slotted screws.

In 1906, Canadian Peter Robertson hit on a head design with a square recess that is still a favorite among many woodworkers (see picture). The Robertson head, however, is today only standard in Canada.

The Phillips head emerged as the choice of the international community. Henry F. Phillips, a Portland, Ore., businessman and former traveling salesman, hit on the idea of an X-shaped socket head. It was initially rejected, but eventually accepted by the American Screw Co., which persuaded General Motors in 1936 to use the Phillips-head screw in manufacturing Cadillacs.
The auto industry soon embraced it, setting the stage for even wider acceptance during World War II. Automakers liked the fact that there is a degree of cam-out or slippage inherent in the Phillips design that allows automated screw-driving machines to pop out once the screw is tight.

The Phillips head screw (a.k.a. the fastener from hell) was invented in the early 1930s by Henry F. Phillips, a Portland, Oregon businessman. He knew that car makers needed a screw that could be driven with more torque and that would hold tighter than slotted screws
he legend goes like this: Sometime around the turn of the century, Peter Lymburner Robertson was setting up a street booth from which he planned to sell tools, when the slot-headed screwdriver he was using slipped out of the screw head and slashed open his hand. "There must be a better way," he vowed to create the ultimate screwdriver. P. L. Robertson did indeed patent his square-headed driver and screw system in 1908. And not long after, the Fisher Body Company (famous for constructing the Ford Model T) decided to use his invention in its production line. The rest is history.

Robertson's colour-coded screwdrivers (green, red and black from smallest to largest) and square-headed screws have grown to dominate the Canadian fastening market: Fully 85% of the screws sold in Canada use the Robertson head. And after a mere 90 years of production, our American cousins are finally keying onto the fact that Robertson indeed created a better driver. About 10% of the screws sold in the U.S. are Robertson and This Old House and New Yankee Workshop guru Norm Abram suggests they could dominate the industry in 15 years.

They never did. They go 'betamaxed'

There's a related story (not that closely, but here is a chance to write about it). The screw standard played an important part in the WWII. Many British tanks and trucks were left stranded in the desert because they used BSW / BSF threads, rather than the world standard Unified UNF/UNC threads. One consequence was a European obsession with adherance to the metric system during post-WWII rebuilding.

In the later half of the second world war all British Military vehicles/Equipment were changed and were made using Unified UNF/UNC threads. This was because of commonality of spares to support the massive amount of equipment being given to the war effort by America. For UNF/C read ANF/C there were only very small technical differences in tolerancing. However, our national standards since the 1870's were British Standard Whitworth and British standard Fine. BSW / BSF These are similar to UNC/U NF but the main differences are the BS use a 55 degree flank and the UN a 60 degree, as do the current ISO Metric threads in Europe. However 1/2" BSW has different pitch to 1/2" UNC as do most of the BSF series. I would strongly recommend that you do not cross mix threads as they will be 20% weaker due to the different thread angles at the very best! Most coarse UNC / BSW threads are used into aluminum and this is where you will have problems with stripping and corrosion particularly with Stainless steel bolts.


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